Camshaft timing belt - removal, inspection and refitting

Engine in-car repair procedures / Camshaft timing belt - removal, inspection and refitting

General information
1 The primary function of the toothed timing belt is to drive the camshaft(s), but it is also used to drive the coolant pump. Should the belt slip or break in service, the valve timing will be disturbed and piston to valve contact may occur, resulting in serious engine damage.

2 For this reason, it is important that the timing belt is tensioned correctly and inspected regularly for signs of wear or deterioration.

Removal
3 Disconnect the battery negative cable and position it away from the terminal.

4 With reference to Section 2, remove the timing belt outer cover and set the engine to TDC on cylinder No1 .

5 If the timing belt is relatively new and is to be refitted later, check to see if it has manufacturers markings to indicate the correct direction of rotation. If none are present, make your own using a dab of paint or typists correction fluid.

Caution: If the belt is refitted differently, accelerated wear leading to premature failure may occur.

6 With reference to Chapter 3, loosen the water pump retaining bolts, then turn the pump body clockwise to relieve the tension from the timing belt. Slide the timing belt from the camshaft sprocket (see illustration).

4.6 Releasing the timing belt from the camshaft sprocket

7 Using an Allen bit, unbolt the auxiliary belt pulley from the crankshaft sprocket. Remove the screws, lift off the timing belt lower cover, then remove the timing belt.

Inspection
8 Examine the belt for evidence of contamination by coolant or lubricant. If this is the case, identify the source of the contamination before progressing any further.

Check the belt for signs of wear or damage, particularly around the leading edges of the belt teeth. Renew the belt if its condition is in doubt; the cost of belt renewal is negligible compared with potential cost of the engine repairs, should the belt fail in service.

Similarly, if the belt is known to have covered more than 60,000 miles, it is prudent to renew it regardless of condition, as a precautionary measure.

9 If the timing belt is not going to be refitted for some time, it is a wise precaution to hang a warning label on the vehicles’ steering wheel, to prevent others from attempting to start the vehicle.

Refitting
10 Loop the timing belt under the crankshaft sprocket loosely, observing the direction of rotation markings.

11 Bolt the lower timing belt cover in position, then refit the auxiliary belt pulley to the crankshaft sprocket and tighten the retaining bolts to the specified torque.

12 Engage the timing belt teeth with the crankshaft sprocket, then manoeuvre it into position over the coolant pump and camshaft sprockets - avoid bending the belt back on itself or twisting it excessively as you do this.

Ensure that the ‘front run’ of the belt is taught - ie all the slack should be in the section of the belt that passes over the coolant pump pulley.

13 With the belt fitted, ensure that the timing marks on the crankshaft pulley and camshaft sprocket are exactly aligned with their corresponding reference marks on the timing belt inner cover; refer to the illustrations in General information for details.

14 Insert a stout screwdriver between the lugs on the coolant pump casting, then using the screwdriver as a lever, turn the coolant pump so that the slack in the belt is taken up (see illustration).

4.14 Adjusting the timing belt tension by rotating the coolant pump

15 Test the belt tension by grasping it between the fingers at a point mid-way between the coolant pump and camshaft sprockets and twisting it; the belt tension is correct when it can just be twisted through 90° (quarter of a turn) and no further (see illustration).

4.15 Testing the timing belt tension

16 When the correct belt tension has been achieved, tighten the coolant pump mounting bolts to the specified torque.

17 Using a spanner or wrench and socket on the crankshaft sprocket centre bolt, rotate the crankshaft through two complete revolutions and reset the engine to TDC on cylinder No1 , with reference to Section 2. Re-check the belt tension, adjusting it if necessary.

18 Refit the timing belt cover and fasten the retaining clips securely.